A device of this type is already known from German patent application 10 2009 049 142.2-16 by the Applicant dated Oct. 12, 2009.
The method of freeze drying is used in the case of thermally sensitive products, such as e.g. pharmaceutical and biochemical products, foodstuffs etc., wherein the product to be dried is initially frozen, crystallized ice is sublimated from the product under vacuum and is precipitated on condensers once again as ice. For this purpose, the pressure, temperature and further parameters of the drying process are controlled and monitored according to a product-specific sublimation pressure curve, in order to achieve reproducible drying results. The energy required for the sublimation is generally supplied by heating.
In many cases, freeze drying systems are designed for intermittent operation and consist predominantly of a drying chamber and a condenser chamber which is connected thereto via a closable opening, wherein the product to be dried is received in a plurality of drying vessels, bottles, ampoules or even trays which are placed on a utility surface inside the drying chamber in order to effect drying. In the drying chamber, a plurality of such utility surfaces are disposed in a frame at a spaced interval one on top of the other so as to be vertically displaceable. Since, in the case of a drying procedure, a large number of drying vessels—each containing a specific quantity of product to be dried—have to be introduced into the drying chamber depending upon the size of the freeze drying system and then have to be removed upon completion of the drying procedure, it is conventional to use automated devices both for loading and unloading the drying vessels, wherein in the case of the systems today it is necessary to establish at the time of ordering whether loading and/or unloading are to be performed manually or by means of corresponding automated devices. Nowadays, it is impossible or very expensive to upgrade a freeze drying plant, which is to be loaded and/or unloaded manually, to an integrated automated process.
In view of the temperature sensitivity of the product to be dried, but in particular owing to the need to produce aseptically perfect conditions in all system components which come into contact with the product to be dried, for the design of a loading and unloading device particular attention must be given to how its configuration and mode of operation appear from a point of view of aseptic production.
The object of the invention is to configure a device of the type presented in the introduction alternatively with respect to the subject matter of the associated main application 10 2009 049 142.2-16 such that in addition to a mechanically simple structure which can also be retrofitted, without significant outlay, on chambers prepared in accordance with the invention, attention is paid in particular to matters of asepsis which means that maintenance and cleaning work can be performed in a convenient manner.
The essential components of the device, namely a carriage and two guides which are independent of the utility surface and on which the carriage is supported, are located inside the drying chamber, wherein the guides form fixed guiding edges on both sides of a movement direction in which loading or unloading takes place, and wherein the carriage forms a movable guiding edge which extends transversely with respect to this movement direction. Depending upon a loading or unloading procedure, the carriage is always movable to a corresponding side of the drying vessels, in order to exert a feeding action. It is particularly advantageous that the guides exert a guiding function upon the drying vessels to be moved and also serve to support the carriage. These components which are preferably encapsulated and formed with smooth walls are easy to clean and should be accessible in particular for steam pressure sterilization but also for other sterilization methods. In each case, the carriage is connected to a drive.
The drive which is allocated to the carriage(s) is formed as a linear motor whose primary part is structurally integrated into the guide of the carriage and whose secondary part which is formed by a sequence of permanent magnets is connected to the carriage. This type of drive is adapted most effectively to the operating conditions of a freeze drying system described in the introduction, as it operates without any friction, maintenance and disruption even under extreme conditions and produces virtually no abrasion. Preferably, two secondary parts are provided, of which in each case one is disposed on the lateral ends of the carriage, wherein the respective primary parts are accommodated in both guides.
The two components, the primary part and secondary part, can also be produced as components which have completely smooth walls on the outer side and whose electromagnetic functional elements are disposed in a hermetically encapsulated manner, so as to permit particularly easy cleaning, in particular sterilization.
The connection, in terms of control engineering, of the primary part(s) of the linear drive, which is allocated to the carriage, by means of an external control located outside the drying chamber can be effected in the simplest case by means of a group of lines which is connected to the guide and is guided via a vacuum-sealed wall passage into the outer space. However, in order to save on the number of lines used, with regard to contamination it is also possible in this respect to provide multiple usage of a line in the sense that it is used for energy transmission and data transmission simultaneously.
Both the carriage and the guides extend in a plane slightly above the plane in which the utility surface is located in the loading or unloading position. In each case, the carriage and the guides form guiding edges which extend perpendicularly with respect to the utility surface and form large smooth bearing surfaces for the drying vessels.
In at least one embodiment, the guides do not form part of the utility surface located in the unloading or loading position and their position can be adjusted relative to one another, i.e. transversely with respect to the said movement direction. Furthermore, they can either be completely displaced in their longitudinal direction which extends in parallel with the said movement direction, or the guides are each formed in a segmented manner, wherein at least individual segments are formed so as to be displaceable. The reason for the displaceability is inter alia to be able to produce a movement of the carriage beyond a loading or unloading opening, so that during an unloading procedure the carriage effects a displacement of the drying vessels from the drying chamber and onto an unloading table available at this location, or during a loading procedure the carriage is movable to a position behind the drying vessels, so that a feeding function can be executed in the direction towards the drying chamber. The reason for the segmentation is also to create gaps in the region of the guides external to a loading or unloading procedure, so that during a drying procedure there are no collisions with parts of the frame which accommodates the utility surfaces in the drying chamber.
In accordance with the features of at least one embodiment, the guides can also be arranged to support two carriages. In this case, unloading and loading can be performed provided that a feeding function is exerted via the one carriage located behind the drying vessels as seen in the respective feeding direction, whereas a counter holding function is exerted via the other carriage. In this manner, the standing stability of the drying vessels is improved whilst cycle times are short.
In accordance with the features of other embodiments, the loading and unloading device comprises a bridge part which is disposed outside the drying chamber, can be moved vertically and optionally horizontally and forms the link to conveying devices located downstream. This bridge part is intended to cooperate with the utility surface located in the unloading position and the guides or segments thereof are displaceable in the longitudinal direction provided that a feeding action as far as to the bridge part can be effected by the carriage.
In accordance with the features of another embodiment, the bridge part can also be used for loading purposes.
In other embodiments, the bridge part is intended for loading purposes and corresponds substantially to the bridge part intended for unloading purposes, i.e., is disposed so as to be movable vertically and optionally horizontally and in a loading position extends in a common plane with the utility surface to be loaded, directly adjoining same. It is essential that even in this case the guides or segments thereof are movable provided that the carriage is movable beforehand to a position behind the drying vessels standing on the bridge part such that a feeding function can be exerted upon them in the direction towards the utility surface. The guides or even segments thereof can be continued by means of segments disposed outside the drying chamber, in order to provide corresponding displaceability of the carriages.
In at least one embodiment, features of the invention serve to improve the displaceability of the drying vessels, particularly in large utility surfaces which accommodate a large number of drying vessels. In particular, it is possible in this manner to make allowance for the situation that the drying vessels are not positioned in an ordered fashion one behind the other but rather with gaps left therebetween, which during a displacement otherwise involves the risk of the drying vessels becoming wedged and toppling over.
In at least one embodiment, features of the invention are directed to an improvement in the accuracy of the positioning of a utility surface e.g. in the loading or unloading position. In general, exact positioning can only be achieved to limited extent merely by using the said plate frame which is to be actuated hydraulically.
A further advantage which arises from the use of the system of supports, in particular the provision of a height position—independent of the frame—of a utility surface resides in the fact that e.g. in the unloading position the vertical distance between the utility surfaces can be adapted to the height of the drying vessels. Sealing the drying vessels in a vacuum by means of rubber stoppers is known, by means of which, after the stoppers have been inserted, they can adhere to the utility surfaces which are located above them in each case, a situation which at the very least hampers ordered extraction from the drying chamber. In contrast, in accordance with the invention a small spaced interval can be adjusted between the rubber stoppers and the utility surface located thereabove and thus extraction from the drying chamber which is not disrupted by adherence of the rubber stoppers.
In further embodiments of the device in accordance with the invention, the second carriage can assume a rest position or can effect a counter holding function on the drying vessels.
It is apparent from the embodiments above that the loading and/or unloading device which is composed of a small number of components which can be handled simply in aseptic terms is also particularly suitable for the retrofitting of existing freeze drying systems in stages. This is aided and abetted by the fact that the components thereof do not come into contact with the utility surfaces.
In particular, it can be provided that the carriage together with the secondary part(s) forms a passive unit which does not have any electrical or mechanical connection to the entire system and can be removed from the guides for cleaning purposes.